“Someone reading a book is a sign of order in the world,” wrote the poet Mary Ruefle. Four centuries earlier, while ushering in a new world order, Galileo contemplated how books give us superhuman powers — a sentiment his twentieth-century counterpart, Carl Sagan (November 9, 1934–December 20, 1996), echoed in his shimmering assertion that “a book is proof that humans are capable of working magic.”

Shortly before his death, Sagan expounded on this passionate conviction in an essay titled “The Path to Freedom,” co-written with Ann Druyan — creative director of the Golden Record project and the love of Sagan’s life. It was published in The Demon-Haunted World: Science as a Candle in the Dark (public library) — the indispensable volume that gave us Sagan on moving beyond us vs. them, science as a tool of democracy, and his increasingly needed Baloney Detection Kit for critical thinking.

With his wide cosmic lens, Sagan places the nascent miracle of the written word in evolutionary perspective:

For 99 percent of the tenure of humans on earth, nobody could read or write. The great invention had not yet been made. Except for firsthand experience, almost everything we knew was passed on by word of mouth. As in the children’s game “Telephone,” over tens and hundreds of generations, information would slowly be distorted and lost.

Books changed all that. Books, purchasable at low cost, permit us to interrogate the past with high accuracy; to tap the wisdom of our species; to understand the point of view of others, and not just those in power; to contemplate — with the best teachers — the insights, painfully extracted from Nature, of the greatest minds that ever were, drawn from the entire planet and from all of our history. They allow people long dead to talk inside our heads. Books can accompany us everywhere. Books are patient where we are slow to understand, allow us to go over the hard parts as many times as we wish, and are never critical of our lapses.

More than a century after Walt Whitman insisted that literature is central to a healthy democracy, Sagan adds:

Books are key to understanding the world and participating in a democratic society.

Echoing Hannah Arendt’s piercing insight into how tyrants use isolation as a weapon of oppression — and what more crushing isolation than to be severed from the life of the mind? — Sagan writes:

Tyrants and autocrats have always understood that literacy, learning, books and newspapers are potentially dangerous. They can put independent and even rebellious ideas in the heads of their subjects. The British Royal Governor of the Colony of Virginia wrote in 1671:

“I thank God there are no free schools nor printing; and I hope we shall not have [them] these [next] hundred years; for learning has brought disobedience, and heresy, and sects into the world, and printing has divulged them and libels against the best government. God keep us from both!”

Considering the complex socioeconomic forces that conspire in constricting opportunity and the powerful way in which books counteract those forces — power to which James Baldwin so beautifully attested — Sagan reflects on his own experience:

Ann Druyan and I come from families that knew grinding poverty. But our parents were passionate readers. One of our grandmothers learned to read because her father, a subsistence farmer, traded a sack of onions to an itinerant teacher. She read for the next hundred years. Our parents had personal hygiene and the germ theory of disease drummed into them by the New York public schools. They followed prescriptions on childhood nutrition recommended by the U.S. Department of Agriculture as if they had been handed down from Mount Sinai. Our government book on children’s health had been repeatedly taped together as its pages fell out. The corners were tattered. Key advice was underlined. It was consulted in every medical crisis. For a while, my parents gave up smoking — one of the few pleasures available to them in the Depression years — so their infant could have vitamin and mineral supplements. Ann and I were very lucky.

With an admiring eye to the example and legacy of the freed slaved turned pioneering social reformer Frederick Douglass, Sagan concludes:

The gears of poverty, ignorance, hopelessness, and low self-esteem mesh to create a kind of perpetual failure machine that grinds down dreams from generation to generation. We all bear the cost of keeping it running. Illiteracy is its linchpin…. Frederick Douglass taught that literacy is the path from slavery to freedom. There are many kinds of slavery and many kinds of freedom. But reading is still the path.

The Demon-Haunted World remains one of the most important books written in the cosmic blink since we first began writing and its central message is, rather sadly, increasingly relevant in our time of unreason. Complement this particular portion with Gwendolyn Brooks on the power of books, Rebecca Solnit on why we read and write, Anaïs Nin on how books awaken us from the slumber of almost-living, and Mary Oliver on how reading saved her life, then revisit Sagan on science and spirituality and this lovely animated adaptation of his famous Pale Blue Dot monologue about our place in the universe.